Field
Apparatuses and methods consistent with exemplary embodiments relate to a polarization light emitting diode (LED) module in addition to a lighting device and a projector having the same, and more particularly to a polarization light emitting diode (LED) module, and a lighting device and a projector having the same, in which a light source and a reflective polarizer are integrated to reduce the size of the lighting device and have a simple structure.
Description of the Related Art
In the related art, a lighting device used in a projector includes a light source; a polarizing beam splitter (PBS) assembly for splitting light emitted from the light source into s-polarized light or p-polarized light; and a polarizing converter for converting polarized light split by the polarizing beam splitter assembly into certain polarized light, e.g. into s-polarized light or p-polarized light.
An extra high pressure mercury lamp, a metal haloid lamp, a xenon lamp, etc. have been commonly used as the light source, but a light emitting diode (LED), of which lifespan is longer and light conversion efficiency is higher than the extra high pressure mercury lamp and the like, has recently been increasingly employed.
However, the amount of light emitted from the LED is less than the amount of light emitted from the extra high pressure mercury lamp and the like. Since a projector is required to include a light source that emits a relatively large amount of light, a plurality of LEDs have been arranged in an array in order to increase the amount of light when the LED is used as the light source for the projector.
When the plurality of LEDs are arranged in an array, the amount of light increases in proportion to the number of LEDs. Further, when the array of LEDs is used for increasing the amount of light, the area (spatial area) of the light source also increases. As the area of the light source increases, a spatial area, in which a light beam entering from a lighting device to a spatial light modulator having a transmission-type liquid crystal display device of the projector, increases. However, it is difficult to effectively use the light beam from the light source with the increased spatial area because there is a limit with respect to an incident angle to the spatial light modulator. Therefore, it may be difficult to effectively use all the light flux from the light source because the spatial area, obtained by multiplying the area of the light source and a solid angle and where the effective light beam is present, i.e. Etendue, is remains constant even though the amount of light is increased by the array of LEDs.
In addition, a lighting device of the related art has a setback that the device is big and complicated because the light source and the polarizing beam splitter assembly are provided separately from each other.
Accordingly, a lighting device and a projector are required to not only increase an efficiency of brightness of light without increasing the Etendue when the plurality of LEDs as the light source are included but also decrease the size of the lighting device and simplify the structure of the lighting device.